This invention relates to apparatus for manufacturing endless needled paper machine felts comprising at least one ply formed by a plurality of overlapping loops of a silver web, comprising a needling machine having a working width corresponding to the width of the paper machine felts to be manufactured and a sliver web feeder which is adapted to be reciprocated throughout the working width of the needling machine.
In the usual manufacture of paper machine felts, a sliver web is reciprocated throughout the width of an endless backing woven fabric and is applied to the latter and is subsequently needled to the backing woven fabric. Because a transverse orientation of the fibers with respect to the direction of travel of the paper machine felt is not desired, it has been disclosed in Laid-open German Application No. 1,660,765 that a more appropriate, longitudinal orientation of the sliver fibers in the longitudinal direction of the sliver web can be achieved in that the sliver webs are trained around two feed rollers so as to form loops, which after the needling operation are axially pulled from the feed rollers so that a tubing is formed, which consists of a ply formed by a plurality of overlapping loops of a sliver web. That known manufacture of paper machine felts has the disadvantage that feed rollers provided with axially aligned conveyor chains are required because the web loops trained around the two feed rollers are pulled off axially, so the structural expenditure is high. Besides, as the felt is pulled off axially, only a single ply of overlapping web loops can be formed so that the fibers have a preferential orientation at an acute angle to the direction of travel of the endless paper machine felt and there is a risk of a distortion by which the running properties of the felt are adversely affected and a formation of wrinkles is promoted.
From German Patent Publication No. 2,324,985 it is known that these disadvantages can be avoided in that a sliver web is supplied to an endless backing woven fabric in its longitudinal direction by means of a feeder which is adapted to be reciprocated throughout the width of the backing woven fabric. In that practice, two or more plies formed by overlapping loops of a sliver web can be applied to the backing woven fabric so that the loops of adjacent plies cross each other. The crossing fiber orientations of these plies ensure that any asymmetry of one ply with respect to the direction of travel of the felt will be compensated so that the running properties and the strength values will be considerably improved, particularly because the loops of the sliver web are needled to a backing woven fabric and the needling machine used for that purpose has a working width corresponding to the width of the paper machine felt to be manufactured. On the other hand, that manufacture of paper machine felts has the disadvantage that sufficiently strong joints between the several loops of the sliver web and between the sliver plies and the backing woven fabric cannot be achieved before the plies of sliver web are needled to the backing woven fabric. This is so because the sliver web which has been applied to the backing woven fabric in loops by means of the feeder is merely forced by means of a pressure roller against the backing woven fabric or against a sliver ply which has been formed before. The adhesion which can be achieved by such contact pressure may permit the sliver web to lift at least locally from its support so that wrinkles may form during the needling operation. The inadequate strength of the joints between the backing woven fabric and the sliver plies promotes also the fixation of wrinkles by the needling operation and the formation of thicker and thinner portions because the sliver plies and the backing woven fabric differ in stretch behavior as portions of the sliver plies can shift relative to the backing woven fabric. For this reason, paper machine felts manufactured by that process have not been successful in practice.